The four third molars, commonly known as wisdom teeth, are the last teeth to develop in the human mouth. Unlike the other 28 adult teeth, their developmental pathway is highly unpredictable and frequently deviates from the standard growth and eruption pattern. The question of whether these teeth can simply stop growing has two distinct answers: the process stalls mid-development, or the tooth never begins to form at all.
The Standard Developmental Timeline
The typical growth cycle for a third molar spans over a decade, beginning long before the tooth is visible. Initial calcification, where the tooth bud starts to mineralize, usually begins around seven to ten years of age. This process involves the formation of the crown, which continues to harden throughout early adolescence. Root development is the next major stage, taking place between the ages of 12 and 18. The force of root elongation helps drive the tooth toward the mouth’s surface, resulting in eruption between 17 and 21 years old.
When Growth Halts: Impaction and Partial Eruption
The most common reason a wisdom tooth “stops growing” is impaction, where the tooth encounters a physical barrier and is prevented from erupting into its correct functional position. This often results from a jaw size-to-tooth size discrepancy, meaning the jaw lacks enough space to accommodate the third molar. Impaction is categorized by the tooth’s orientation. For example, a mesial impaction angles the tooth forward toward the second molar, while a horizontal impaction means the tooth lies completely sideways. A tooth may also become partially impacted, where only a portion of the crown breaks through the gum tissue, creating a flap known as an operculum.
When Growth Never Starts: Dental Agenesis
A separate scenario from impaction is dental agenesis (or hypodontia), where the wisdom tooth bud fails to develop in the first place. This represents a complete genetic failure to form the tooth rather than an arrest in growth. Third molars are the most frequently missing teeth in the human dentition, a trend linked to human evolution and a reduction in jaw size. Agenesis is primarily determined by genetic factors, with specific genes like MSX1 and PAX9 implicated in controlling tooth development. The absence of one or more third molars due to agenesis is generally a variation of normal development and often presents no clinical complications.
Monitoring and Clinical Management
When wisdom teeth fail to erupt, clinical management is necessary. For teeth that have failed to erupt, a dentist will use periodic X-rays, such as panoramic radiographs, to monitor the tooth’s position and surrounding bone structure. The decision to intervene is driven by the potential risks associated with the retained tooth.
Risks of Impaction
Impacted teeth can lead to several pathologies, even if they are not causing pain. A partial eruption can create a pocket for bacterial accumulation, leading to infection and inflammation known as pericoronitis. Fully impacted teeth carry a risk of developing cysts from the tissue sac that surrounds the unerupted crown. These cysts can damage the adjacent second molar’s roots or the jawbone.
Treatment Options
If the tooth is asymptomatic but poses a high risk for future problems like decay or root damage, surgical extraction is often recommended to prevent these complications. Conversely, if a fully impacted tooth remains stable and asymptomatic, a strategy of active surveillance may be chosen instead of removal.